of an Electric Charge by Gases. 



195 



tinfoil to the knob, the condenser can be discharged. While an 

 unexhausted vessel does not act as a condenser (any slight charge 

 upon the knob being removed by earthing) it was found that if 

 exhausted after charging, a discharge could be obtained. The 

 knob of the unexhausted condenser was put in connection with 

 the Wimshurst for a few seconds, then earthed to remove any free 

 charge. It was then rapidly exhausted to about \ cm. pressure, 

 and on joining the tinfoil to the knob, a discharge almost as strong 

 as though the vessel had been exhausted at first was obtained. 

 Several residual discharges could be obtained. 



If the pressure were not rapidly reduced, the charge leaked 

 away, but with large condensers, and by working in a very dry 

 room, a discharge could be obtained after many hours. If the vessel 

 was exhausted before charging, then the charge has remained 

 more than twelve hours. 



Since a vacuum would thus act as a conductor, it was thought 

 that a condenser might be constructed without any metallic 



Fig. 2. 



coatings. This was realized by making a tube of the form of 

 Fig. 2. The two chambers have no connection with each 

 other, and could be exhausted simultaneously by one pump 



